Subscribe to Spaceflight Now Plus for access to our extensive video collections!How do I sign up?Video archiveSTS-120 day 2 highlightsFlight Day 2 of Discovery's mission focused on heat shield inspections. This movie shows the day's highlights.
PlaySTS-120 day 1 highlightsThe highlights from shuttle Discovery's launch day are packaged into this movie.
PlaySTS-118: HighlightsThe STS-118 crew, including Barbara Morgan, narrates its mission highlights film and answers questions in this post-flight presentation.Full presentationMission filmSTS-120: Rollout to padSpace shuttle Discovery rolls out of the Vehicle Assembly Building and travels to launch pad 39A for its STS-120 mission.
PlayDawn leaves EarthNASA's Dawn space probe launches aboard a Delta 2-Heavy rocket from Cape Canaveral to explore two worlds in the asteroid belt.Full coverageDawn: Launch preview
These briefings preview the launch and science objectives of NASA's Dawn asteroid orbiter.Launch | ScienceBecome a subscriberMore video

Coloured quasars suggest ‘smoky’ Universe

KULVINDER SINGH CHADHA

ASTRONOMY NOW

Posted: 27 February, 2009

Hold your breath: we may be living in a smoky Universe that dims light from distant objects such as quasars, or so say astronomers working on the Sloan Digital Sky Survey (SDSS).

Just like when a sunset appears reddened because it has to travel through more of Earth’s atmosphere, light from quasars could appear redder because it has to travel through the dust of intervening galaxies. “Galaxies contain lots of dust, most of it formed in the outer regions of dying stars,” says study team leader Dr Brice Menard of the Canadian Institute for Theoretical Astrophysics. “The surprise is that we are seeing dust hundreds of thousands of light years outside of the galaxies – in intergalactic space.” The team’s findings have been published in the Monthly Notices of the Royal Astronomical Society.

Dust in galaxies often drifts off to mix with interstellar gas. The new analysis of quasar colors shows that galaxies also expel dust to distances of several hundred thousand light years. Image: Sloan Digital Sky Survey.

Using images from SDSS 2, the team analyzed 100,000 distant quasars, which were located behind at least 20 million galaxies. “Putting together and analyzing this huge dataset required cutting-edge ideas from computer science and statistics,” says team member Gordon Richards of Drexel University. “Averaging over so many objects allowed us to measure an effect that is much too small to see in any
individual quasar.”

Why could this ‘haze’ be filling the Universe instead of remaining in its galactic confines? There are two theories. In one, supernovae explosions and strong winds from massive stars push gas and dust out of galaxies. In the other theory, this process occurs by radiation pressure on the dust by starlight. “Our findings now provide a reference point for theoretical studies,” says Menard.

Whatever the mechanism that drives dust out into intergalactic space, its presence there could be a problem. Cosmological observations that make use of distant quasars and supernovae to gauge the size and age of the Universe, as well as the presence of the mysterious ‘dark energy’ (thought to be responsible for the expansion of the Universe) could be affected. However, Menard says that the presence of dust doesn’t remove the need for dark energy and that any estimates would merely have to account for the dust. He adds, “These
experiments are very ambitious in their goals and subtle effects matter.”

The PlanetsFrom tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets. GET YOUR COPY

Hubble RebornHubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts. GET YOUR COPY

3D UniverseWitness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D! GET YOUR COPY